This invention relates to the centrifugal separation of the heavier and lighter phases of whole blood and is concerned particularly with a blood container assembly suitable for the centrifugal separation operation and having an improved capacity for preventing migration and remixing of the separated blood phases.
A type of centrifugal blood separation assembly known in the art employs a glass tubular container having therein a body of gel-like barrier material which, upon centrifugation, will form a transverse barrier between the lighter and heavier phases of whole blood, e.g., the lighter liquid and heavier, substantially cellular phases. For example, U.S. Pat. No. 3,780,935 discloses such a system in which barrier material is injected into a blood collection container during centrifugation. For somewhat similar disclosures, see also U.S. Pat. Nos. 3,976,579 and 3,986,962. U.S. Pat. 3,852,194 deals with apparatus which differs from that disclosed in U.S. Pat. No. 3,780,935 in that the barrier material is loosely disposed within the bottom of a tubular collection chamber.
In U.S. Pat. No. 3,920,549, gel-like barrier material is loosely disposed within a tubular blood collection chamber and an energizer device is used to influence the flow of the material during centrifugation, causing it to flow along the inner surfaces of the collection chamber. It is further disclosed that the inner surface of the collection chamber may be coated with a lubricant, such as a polyethylene oxide polymer, to prevent adhesion of blood thereto. Lessened adhesion of the blood to the inner surface reduces the likelihood of rupturing of red blood cells due to collision of the barrier material with red blood cells which have adhered to the inner surface.
Although the use of a gel-like material to create a barrier between the centrifugally separated phases of whole blood has proved to be a beneficial approach, certain problems still exist. One such problem is leakage past the barrier of one blood phase into the other. With the equipment available prior to the present invention, such leakage was observed after extended periods of time and, particularly, in instances where the collection chamber was placed on its side.